Method of and hydraulic press for inserting bushings



E. K. MORGAN Jam 15, 1935.

METHOD OF AND HYDRAULIC PRESS FOR INSERTING BUSHINGS Filed April 28,1952 5 Sheets-Sheet l O w w /w 0 M O O M m 3 I WM H O n W H UNI Z 0 FlH| l HH h l I l O H. G IIIIIIII, M O O F C Lllfil T n 1 1 Jan. 15, 1935.E. K. MORGAN METHOD OF AND HYDRAULIC PRESS FOR INSERTING BUSHINGS FiledApril 28, 1952 5 Sheets-Sheet 2 Jan. 15, 1935. E. K. MORGAN 1,987,862

METHOD OF AND HYDRAULIC PRESS FOR INSERTING BUSHINGS Filed April 28,1932 5 Sheets-Sheet 5 ,F za Liiiiii'ffffi:If @00000 00mm? iim H llllilJan. 15, 1935. E. K. MORGAN METHOD OF AND HYDRAULIC PRESS FOR INSERTINGBUSHINGS Filed April 28, 1932 5 Sheets-Sheet 4 Jan. 15,1935. E. K.MORGAN 1,987,862

METHOD OF AND HYDRAULIC PRESS FOR INSERTING BUSHINGS Filed April 28,1932 5 Sheets-Sheet 5 Patented Jan. 15, 1935 METHOD OF AND HYDRAULICPRESS FOR INSEBTING BUSHINGS Everette K. Morgan, Rockford, Ill.,assignor to The Ingersoll Milling Machine 11]., a corporation ofIllinois 00., Rockford,

Application April 28, 1932, Serial No. 608,040

19 Claims.

This invention relates to a novel method of and an hydraulic press forinserting bushings,

such, for example, as the valve guide bushings in internal combustionengines.

The insertion of valve guide bushings with the correct press fit ishighly important for the reason that a loose bushing will usually workupwardly, sometimes to such an extent as to actually hold a valve open.Even where the bushing does not move that far, its movement out ofposition destroys its further use as a pilot for the end of the valvespring, so that the spring can work sidewise and make the valve stembind and cause faulty engine performance. operated at high speeds, as inthecase of airplanes and automobiles, are found to be particularlysubject to troubles arising from loose valve bushings, and many aircasualties are directly traceable to such engine troubles. With the oldmethods employed for inserting bushings, and either testing their fitafter insertion by tapping the same with a hammer, or relying on thejudgment of the workman as to whether the same is tight enough. simplyby noting whether the bushing can be driven home easily or not,,therewas manifestly no real certainty as to the correct press fit of bushingsin an engine block. It is, therefore, the principal object of myinvention to insert bushings according to a new method in which eachbushing is inserted by means of a plunger carried in a head andsubjected to a given yielding pressure, whereby in the movement of aworkcarrying platen toward the head to detect the loose fit of bushingsby their failure to overcome the yielding pressure and produce backupmovement of the plungers in the head in the stroke of the platen. Withthis method it is manifestly possible to insert the entire set ofbushings in a block, or at least a plurality of bushings simultaneously,and the loose bushing or bushings are indicated in the manner stated andmarked for replacement.

It is another important object of my-invention to provide an improvedhydraulic press adapted for inserting bushings in accordance with theabove method. ,A special feature of this press is the provision of aretractible stop for limiting the initial movement of the platen so thatloose bushings can be marked before final movement of the platen topress all of the bushings home. This makes it possible to operate onshoulder type bushings which wouldotherwise .be diiflcult to handle,because of the fact that their movement is limited by the shoulder.Plain bushings'do not require special handling because a loose bush-Engines ing of that type will be pressed an appreciable distance beyondits working point so that it is apparent at a glance that its fit is notsufllciently close to the set standard.

Still another object consists in the provision of signals or telltalesfor automatically indicating the loose bushings, whereby to avoid anyguesswork.

The invention embraces other objects and advantages which will appear inthe course of the following detailed description, in which reference ismade to the accompanying drawings, wherein-- Figure 1 is a front view ofa press made in accordance with my invention;

Fig. 2 is a fragmentary side view partly in vertical section showing thepedal-operated valve controlling the operation of the platen;

Fig. 3 is an enlarged vertical sectional detail illustrating theoperation of the machine in the insertion of a bushing having thecorrect press fit;

Fig. 4 is a similar view illustrating the operation in the case of aloose bushing;

' Figs. 5 and 6 are-views corresponding to Figs. 3 and 4 but showing theoperation upon plain bushings as distinguished from the shoulderedbushings appearing in the other views;

Fig. 7 is an enlarged view of a portion of the head of the machinepartly in front elevation and partly in vertical section .to show howthe loose bushings in a set are indicated so as to single them out fromthe others; p Fig. 8 is a horizontal section on the line 8-8 of Figure 1mainly to show the retractible stop and the operating means therefor;

Fig. 9 is a vertical sectional detail on the line 9,9 of Fig. 7 tofurther illustrate the stop;

Fig. 10 is a horizontal section on the line 10-10 of Figure 1 showingthe engine block in plan and illustrating part of the block locatingmeans and electric circuit control;

' Fig. 11 is a plan view of the dowel pin operating means;

Fig. 12 is a sectional detail on the line 12-42 of Fig. 10 illustratingthe operation of the dowels;

Fig. 13 is a view on the line 13-43 of Fig. 10 illustrating theelectrical control provided in connection with the dowel operatingmeans, and

Fig. 14 is an oil and electrical circuit diagram for the press.

Similar reference numerals are applied to corresponding parts throughoutthe views.

While the present invention has particular reference to the insertion ofshouldered valve guide bushings 10 or plain valve guide bushings 10 ininternal combustion engineblocks 11, it will soon be apparent that theinvention is not limited to this special work but is adapted for theinsertion of any kind of bushings, or for that matter any parts which itis important be inserted with the correct press fit. The operationherein illustrated and described should, therefore, be taken as merelyone example of many possible applications of the invention. Furthermore,while I have illustrated the use of a hydraulic medium, or, morespecifically, the combination of an hydraulic and a pneumatic medium toafford only a predetermined pressure on the plungers for inserting thebushings and allowing the plungers to back up when the pressure thereonis overcome as a result of the tight fit of the bushing, it will also beapparent that a similar result would be obtained by means of suitablesprings. In other words, it is only essential that the plungers beyieldable at a predetermined pressure, and any means suitable foraccomplishing that purpose comes properly within the purview of myinvention.

Referring now principally to Figure 1, the numeral 12 is applied to thebase of the press which has side columns 13 supporting a horizontal heador cross rail 14. Guides 15 on the columns 13 have a work carryingplaten or table 16 slidable thereon for vertical movement toward andaway from the head. A plunger 17 extends downwardly from the platen intothe working cylinder 18 in the base for movement with the double-actingpiston 19 operating in the cylinder. 20 is an apron depending from theplaten simply to enclose the upper end of the cylinder and the plunger,for the sake of appearance. The head 14 carries plungers 21 on whichholders 22 are provided for the valve guide bushings 10 or 10', as thecase may be. The holders 22 are stems made to fit snugly in the bushingsand having any suitable means for frictionally gripping the same. In thepresent case the lower ends of the -stems are shown as split andslightly spread to provide the desired frictional hold on the bushings.From this much description it will be seen that a set of bushings can beplaced on the holders 22 in alignment with the suitably reamed holes 23provided therefor in the engine block 11, and then inserted by an upwardmovement of the platen 16 under hydraulic pressure applied to the piston19. The holders 22 in the return of the platen will, of course, slip outof the bushings, leaving them in place in the block. The holes 23 are,of course, all reamed at one time in a multiple spindle machine. Thereis, however, a certain amount of variation in the size of these holesdue to the difiference in the reamers. On the other hand, the bushingsto be inserted in these holes are all machined within a certaintolerance. Naturally, then, a medium sized bushing when entered in amedium sized hole will have the correct press fit, but a small sizedbushing, that is, one below medium size, will undoubtedly be too looseif entered in a hole above medium size. There is no objection tobushings having something above a correct press fit, but there is adecided objection to a bushing having anything below a correct pressfit, as indicated above. The purpose of the present invention, as willsoon appear, is to indicate which bushings are loose, that is to say,arebelow a correct press fit.

Referring to Figs. 1, 2. '7 and 14, it will be seen that oil isdelivered to the lower end of the cylinder 18 through a pipe 24 from apump by shifting the valve 26 by means of a foot pedal 27. A compressionspring 28 cooperates with one end of the valve to normally hold it inthe position illustrated in Fig. 2, in which the delivery is through thepipe 29 to the upper end of the cylinder 18 to return the platen 16 tothe lowermost position. In other words, the depression of the pedal 27takes care of the raising of the platen, and it is only necessary torelease the pedal to secure the return of the platen. The pump 25 iscontinuously operated by means of the electric motor 30 so long as thepress is in use.

As best appears in Figs. 3-7, the head 14 is cored out to provide an oilpressure chamber 31 and an air chamber or accumulator. 32 to afford aplace for the oil to back up when the plungers 21 back up in the headagainst the pressure of the oil in the chamber 31, due to the resistanceto movement of the bushings into their holes, as will soon appear. Theoil in the chamber 31 is maintained at a predetermined pressure bycommunication with the pump 25 through the line 33 and check valve 34(see Fig. 14). The plungers 21 project through stuifing boxes 35 intothe chamber 31 and, hence, are normally urged outwardly under thepressure of the oil in said chamber. Outward movement, however, isprevented by reason of stems 36 extending upwardly from the plungers 21through holes 37 in the top wall of the chamber 31 and having nuts 38threaded on the projecting ends thereof for abutment with said wall. Anyother suitable means could be provided for holding the plungers againstoutward movement. A chamber 31 has the stems 36 projecting into it andany leakage past the stems from the chamber 31 is conducted from thechamber 31' through a pipe 39 back to the sump of the pump 25. Nuts 40are threaded on the plungers 21 outside the chamber 31 in apredetermined spaced relation to the gland nuts 41 on the stuifingboxes. This is to limit the inward movement of the plungers when thebushings have the correct press fit in their holes and accordinglyovercome the pressure of the liquid in the chamber 31. The nuts 40 inthe case of a plain bushing, like the bushings 10' shown in Figs. 5 and6, are set so as to allow a predetermined backing up of the plungersunder resistance of the bushings, so that when the platen 16 is given apredetermined stroke, the bushings which have the proper press fit willbe inserted to the correct distance, as shown in Fig. 5, whereas thosebushings which are so loose that they do not afiord sufiicientresistance to cause the plungers to back up in the manner stated will beinserted to an abnormal distance. Naturally, if the setting of the nuts40 is made for enough movement of the plungers 21, the loose bushingscan be indicated simply by the extent to which they will project belowthe line of bushings that have the correct press fit. However, I preferto provide some definite means for indicating those bushings whichbecause of their loose fit, should 'be replaced. A signal or telltalemeans for this purpose is indicated generally by the reference numeral42. It consists of an elongated housing 43 suitably provided on the head14 in front of the row of plungers 21 and having electric lights 44mounted therein behind windows 45. Switches 46 in the housing arenormally held closed by compression springs 47 to complete electriccircuits through the lights, as indicated in Fig. 4.

Small push rods 48 project from the back of the housing 43 toward theplungers 21 for operation thereof by means of cam-shaped projections 49provided on the plungers. The projections 49 are so located with respectto the push rods 48 to leave the switches 46 closed so long as theplungers 21 have not been backed up by the bushings associatedtherewith. Thus, in Fig. 5 it will be observed that the cam-shapedprojection 49 has depressed the push rod 48 so that there is no lightappearing at the window 45. This indicates there is nothing wrong withthe fit of this particular bushing, but in Fig. 6 it will be noticedthat the projection 49 has not depressed the push rod 48 in theup-stroke of the platen 16, owing to the fact that the plunger 21 wasnot backed up against the pressure of the liquid in the chamber 31 bythe bushing, the latter not having the correct press fit. Consequently,the light appears at the window and indicates the necessity forreplacement of this particular bushing. I make reference only to Figs. 5and 6 at this point because of the fact that a two-stage operation isused in the case of the shouldered bushings illustrated in Figs. 3 and4, which requires some further explanation. It will suflice at thispoint to state that at the commencement of the up-stroke of the platen16, all of the windows 45 will be illuminated since all of the switches46 are closed at that time. If any one of the lights is defective, it isimmediately apparent to the operator and given attention so that he canrely later upon the lights for indication of the loose bushingsrequiring replacement. Near the end of the up-stroke the plungersoperating on loose bushings will have their cam projections ride overthe push rods 48 thus momentarilyputting out the lights associated withthe loose bushings, and at the end of the stroke of the platen the camprojection 49 on those plungers operating on bushings having the correctpress fit will depress the push rods associated therewith and,consequently, the only lights that will appear will be those associatedwith the plungers operating on loose bushings.

The shouldered bushings require a two-stage operation, in the firststage of which an indication will be given of the loose bushings, and inthe second stage of which the bushings will be set home. This operationis secured by providing stops 50 projecting downwardly from the head 14for engagement with the cylinder block, as illustrated in Figs. 7 and 9.The stops are of plunger form having enlarged upper ends 51 received inbores 52 in the head and retained by bushings 53 fitting about the samebelow the en-, larged ends. Nuts 54 are threaded on the projecting endsof the plungers and fixed in adjusted position by set screws 55, wherebyto limit upward movement of the plungers. Retractible stop members 56are provided, which, in their op-. erative position, serve to hold thestops 50 extended, as shown in Fig. 9, with the nuts 54 in apredetermined spaced relation to the bottom of the head. The members 56are notched out, as at 57, so that when they are moved to retractedposition with these notches in register withgthe plungers the latter arefree to back into their bores far enough for the nuts 54 to limit theirmovement (see Fig. 5). The bottoms of the notches are inclined and theupper ends of the plungers are correspondingly inclined, as indicated at58, to permit movement of the members 56 to operative position, that is,from the retracted position shown in Fig. 5 to that shown in Fig. 9, bythe turning of pinions 59 meshing with rack teeth 60 formed in themembers 56. The pinions 59 are mounted on a shaft 61 received insuitable bearings 62 on the head 14 and having a central operatingpinion 63 mounted thereon at the middle thereof. A rack 64 meshes withthe pinion 63 and is operated by a piston 65 in a cylinder 66 mounted-onthe bottom of the head 14 at the back thereof (see Fig. 3). Oil underpressure is delivered toeither end of the cylinder 66 from the pump 25by operation of a pilot valve 67, which is suitably mounted on the sideof the press, as shown in Figure 1. A hand lever 68 is shown foroperating the valve and, while I have not disclosed any means forholding the lever 68 normally in one position to keep the stop members56 in operative position, it should be understood that it would notrequire anything more than a spring urging the lever to move in one,

direction against a stop to secure that result. However, since the presswill be used interchangeably for operation on plain bushings orshouldered bushings, I prefer to leave the operation of the valve 67entirely up to the operator, to be moved selectively to either position.In Fig. 14, it is clear that the pipe 69 delivers oil under pressure tothe valve 67 from the pump 25 and if the valve is moved from a neutralposition to the position shown, oil is delivered in front of the piston65 to move the same to the position illustrated, whereby to hold thestopmembers 56 in operative position. Oil from behind the piston is drainedto the sump of the pump 25 through pipe 70. When the stop members 56 areto be retracted the valve 67 is moved the other way from neutralposition so as to' deliver oil from the pipe 69 behind the piston 65,the oil from in front of the piston being then drained through the pipe'71 to the sump. In operation, assuming that the valve 6'7 is in theposition shown in Fig. 14, holding the member 56 in operative position,it is clear that the upward movement of the platen 16 with the engineblock 11 will be limited, as indicated in Fig. 9. At this time, theloose bushings are indicated, as shown in Figs. 4 and "I, by means ofthe lights at the windows associated therewith, all of the other windowsassociated .with the bushings having the proper press fit beingunlighted, as indicated in Figs. 3 and '7. The operator will, therefore,simply mark-the loose bushings requiring replacement. Then, withoutreleasing foot pressure on the pedal 27, the operator will simply movethe lever 68 to its opposite limit whereby to retract the stop members56. and allow further upward movement of the block 11 with the platens16 to set all of the bushings home, the loose ones along with the tightones. Afterward, when the block 11 is removed from the press the markedbushings are driven out and bushings of the proper size to fit the holesare entered.

Referring now to Figures 1 and 10-14, it will be observed that theengine block 11 is arranged to be located accurately on the platen 16 bymeans of a plurality of dowels 72. Two are sufiicient, although I haveillustrated four, one at each corner. It is, of course, important tohave the block accurately located because it would make it necessary toreplace the spindles or plungers 21 if the platen 16 were raised with anengine block improperly positioned thereon. The dowels are guidedthrough accurately ground bushings 73 in accurately located bores 74provided there- Y LU for in the platen 16. Rack teeth 75 are formedbeveled gears'80 on a transverse shaft 81 arranged to be turned by meansof a hand lever 82. It is,

I therefore, clear that all of the dowel pins 72 are raised or loweredsimultaneously by operation of the lever 82, the pins being raised byclockwise movement of the lever and lowered by counterclockwise movement(see Fig. 11) Now, in order to insure, first of all, that a block 11 hasbeen placed on the platen, and secondly, that the dowel pins 72 havebeen raised to properly locate the block, before the pedal 2'? isdepressed to raise the platen, I have provided two control switches 83and 84 connected in series with a solenoid 85. The solenoid 85 has anarmature 86 which, so long as the solenoid is not energized, is disposedin its lowermost position in the path of a lever 87 arranged to beoperated by the pedal 2'7 to shift the valve 26, whereby to prevent suchoperation. The switch 83 is normally held open by a spring 83 and has aplunger 89 projecting therefrom for engagement by a portion of the blockwhen the latter is placed on the platen 16 in abutment with stops 90,which are provided to roughly position the block. In this way, theswitch 83 is closed when the block is placed on the platen inapproximately the right position. The switch 84 likewise has a spring 91normally holding the same in open circuit position, and a plunger 92projects from the switch in the path of movement of an adjustable setscrew 93 provided on a lug 94 formed on the hub of the lever 82, asclearly appears in Fig. 13, so that the switch is arranged to be closedwhen the lever 82 is moved in a clockwise direction from a substantiallyhorizontal position to a substantially vertical, limit position. In thatway, the circuit iscompleted through the two switches 83 and 84 toenergize the solenoid85 and raise the armature 86 to retracted positionwith respect to the lever 87, so that the pedal 27 can be depressed. Thespindles of the press are, therefore, fully protected against jamming.

The pump is known as the Oilgear QW pump which is no doubt covered in acopending application filed by The Oilgear 00., Milwaukee, Wisconsin. Itwill, therefore, sufiice for the present purposes to state that the samecomprises a gear pump section 95 and a piston pump section 96,preferably inside a single housing. The piston pump in the QW pumphappens to be what is known as a self-centering pump because of itsbeing arranged to build up to a predetermined pressure in the line andthen automatically shift to a position of little or no delivery, wherebyto merely maintain the predetermined pressure and no more. However, thatphase of the piston pump is of no special significance so far as thepresent invention is concerned, and the circuit diagram has not beencomplicated by a showing of that feature; so far as the presentoperation is concerned the piston pump need not be selfcentering,because a blow-off valve could be provided to open at the predeterminedpressure so as to by-pass excess oil to the sump. The sump is indicatedat 9'7. 98 indicates a suction line leading from the sump to the gearpump 95, and it will be observed that the gear pump primes the pistonpump by delivery thereto from the discharge line 99. The piston pumpdischarges through a line 100 communicating with the pressure port 101of the valve 26. The valve 26 determines by its position whether the oilis delivered to the line 24 or the line 29. Assuming that the valve 26is in the position shown in Fig. 14, the delivery is to the line 29 tothe upper end of the cylinder 18 to lower the platen by means of piston19. The oil below the piston is drained through line 24 back to thevalve, and from there through line 102 leading back to the dischargeside of the gear pump so as to be delivered to the intake of the pistonpump, or, if there is an excess of oil, to be returned to the sumpthrough the line 103 and a low pressure relief or footvalve 104. Thelatter offers sufiicient back pressure on the piston to insure smoothoperation. When the piston 19 has moved as far as it will go, pressurein the line 100 builds up until it overcomes the high pressure reliefvalve 105 which then allows drainage to the sump through the line 106.On the up-stroke of the piston 19, when the valve 26 delivers oil fromthe pressure port 101 to the line 24, the foot valve 104 offerssuiiicient back pressure on the piston 19 in the drainage of oil fromabove the piston to insure smooth operation. The valve 26 is shown inposition for delivering oil to the upper end of the cylinder 18 so as tokeep the platen in lowered position, that being the normal position ofthe valve secured by action of the spring 28.

It is believed the foregoing description conveys a good understanding ofthe objects and advantages of my invention. The appended claims havebeen drawn to cover all legitimate modifications and adaptations.

The mechanism herein disclosed for insuring proper positioning of thework piece prior to operation of the tools therefrom forms the subjectmatter of a copending divisional application Serial No. 668,519, filedApril 29, 1933.

vI claim:

1. The method herein descibed which consists in entering parts in holeswherein they are to I have a press fit. then testing the parts for thecorrectpress fit by determining whether it takes at least apredetermined minimum pressure to move them in the holes, and thenpressing the parts into the holes, so that the parts having more than aminimum fit are moved a predetermined distance in the holes, and so thatthose parts having less than a minimum fit are moved a differentdistance in the holes to give a loose fit indication.

' 2. The method herein described which consists in entering a part in ahole wherein it is to have a press fit, testing it for the correct fitby starting it into the hole with a pressure member adapted to yieldwhen anything above a predetermined pressure is exerted thereon, andthen pressing it farther in the hole the full distance desired.

3. The method herein described for press fitting parts and detectingfaulty fit of any one or more of a plurality of parts adapted to have apress fit in holes therefor, which consists in entering the partssimultaneously in the holes therefor, then simultaneously pressing theparts a certain distance into the holes but by partially independentoperation upon each testing all of the parts for correct press fit bydetermining whether it takes more than a predetermined min- .imumpressure to move each individual part in the hole therefor.

4. The method herein disclosed for detecting faulty fit of any one ormore of a plurality of parts adapted to have a press fit in holestherefor, which consists in entering all of the parts simultaneously inthe holes therefor, and simultaneously testing the parts for correctpress fit by pressing the same into the holes with members each adaptedto yield when anything above a predetermined pressure is exertedthereon, and then pressing the parts into the holes.

5. The method of inserting press fit parts such as bushings into holeswhich consists in simultaneously entering a plurality of such parts intothe holes therefor, andpressing the parts into place with members eachadapted to indicate individually the part, which presses into place withless than a predetermined pressure applied.

6. The method of inserting press fit parts such as bushings so as todetect those'liaving a loose fit, which consists in pressing the partsinto their holes with members yieldable when more than a predeterminedthrust .is exerted thereon, whereby to indicate less than a minimum fitof any part or parts which fail to cause the members associatedtherewith to yield.

7. The method herein described which consists in entering parts in holeswherein they are to have a press fit and wherein they are to be enterednormally a certain distance, testing the parts for the correct press fitbefore pressing the same in the full distance, by pressing the partsinto the holes only partway and in such a manner as to indicate whetherit takes more than a predetermined minimum pressure to move them in theholes, then suitably marking for subsequent removal the parts which givea loose fit indication, and finally pressing all of theparts into theholes to a predetermined point.

8. A machine of the class described comprising a work support, a toolsupport, one of said supports being movable toward and away from theother, a plurality of holders on the tool support for maintaining inalignment parts to be entered with a press fit in holes in the work,means yieldably supporting the holders in a predetermined position onthe tool support, the same permitting a predetermined amount ofretrograde movement of the holders individually when more than apredetermined thrust is exerted thereon, and means for positively movingthe movable support.

9. A machine as set forth in claim 8 including means for indicatingwhich holders have been given retrograde movement. I

10. A machine of the class described comprising a work support, a toolsupport, one of said supports being movable toward and away from theother, a plurality of holders on the tool support for maintaining inalignment parts to be entered with a press fit in holes in the work,plungers mounted for retrograde movement on the tool support with theholders, means yieldable at a predetermined pressure and serving to holdthe plungers in a normal position with respect to the tool support,whereby to permit retrograde movement of the holders when more than apredetermined thrust is exerted thereon, and means for positively movingthe movable support.

11. A machine as set forth in claim 10 including means on the toolsupport for indicating which of the plungers have been given retrogrademovement. r

12. A machine of the class described comprising a work support, a toolsupport, one of said supports being movable toward and away from theother, a plurality of holders on the tool support for maintaining .inalignment parts to be en tered with a press fit in holes in the work,plungers slidably received in holes provided therefor on the toolsupport for retrograde movement with the holders, said tool supporthaving a fluid pressure chamber provided therein communicating with saidholes whereby to hold the plungers extended toa predetermined positionunder a predeter- -mined fiuid pressure, and means for positively theother, a work holder onthe tool support for.

holding in alignment 9, part to be entered with a press fit in a hole inthe work, a plunger mounted on the tool support for retrograde movementwith the work holder, means yieldable at a predetermined pressure forholding the plunger in extended relation to the tool support, means topositively limit the retrograde movement of said plunger, and means forpositively moving the movable support.

16. In a=machine of the class described, the combination of a worksupport, a tool support, the one support being movable toward and awayfrom the other, a holder on the tool support for holding in alignment apart to be entered with a press fit in a hole in the work, a plungermounted on the tool support for retrograde movement with the holder, achamber containing a pressure fluid medium on the tool support forholding the plunger in extended position relative to the tool support,whereby to permit retrograde movement when a predetermined thrust isexerted on the plunger, means for positively limiting the retrogrademove-' ment of the plunger, and means for positively moving the movablesupport.

17. A machine as set forth in claim including means for indicating whenthe plunger is given retrograde movement.

18. A machine as set forth in claim 15, wherein the movement of themovable support is normally limited by engagement with a stop, themachine including a retractable stop member arranged to engage the stop,whereby to provide for less movement of said support when desired.

'19. A machine for inserting a part with a predetermined press fit intoa hole in a work piece having, in combination, two members mountedforrelative movement toward and away from each other in the direction ofthe axis of said hole when the'work piece is mounted on one of themembers, an abutment on the other member engageable with one end of thepart to transmit pressure thereto for forcing the part into said hole inthe movement of said members toward each other;

and means yieldable under a predeterminedpressure for holding saidabutment against movement relative to its supporting member until saidpressure has been overcome in the entry of the part insaid hole,yielding of said abutment during entry of thepart into the holeconstituting an indication of the proper fit.

EVERE'I'I'E K. MORGAN.

